The Complete Naturalist

Birds present the amateur naturalist with some of his or her greatest challenges, for the simple reason that they cannot differentiate between the well-meaning naturalist and the life-threatening predator. So their first instinct is to put as much space as possible between us and them. The same is true of mammals, of course, but birds have the extra disadvantage from the naturalist’s point of view of being blessed with wings, making them flighty masters of three dimensions.

Having said that, birds do tend to be visible. Step off a plane into a new and exciting country and the first living things you see when leaving the airport are birds. But catching brief glimpses and getting long, protracted views of them doing what birds do when they are not flying around airports are two totally different ball games! Another important and user-friendly aspect of birds is that many of them vocalise as part of their everyday pattern of behaviour. Generally speaking they are much noisier than mammals, although this behaviour can be seasonal and related to breeding or to environmental conditions.

That’s what the great Victorian biologist Thomas Huxley called birds and, though to the naturalist they present many of the same challenges as do mammals, it may come as a surprise to learn that birds are closely related to reptiles. Some scientists think the two groups have so much in common that they put them in the same class, the Sauropsida.

Of all the terrestrial vertebrates, birds are the most numerous, with something like 9,000 species – there are about twice the numbers of feathered animals as there are furred! In recent years birdwatching has reached the masses and is huge business in Europe and America, with countless societies dedicated to watching and studying them (in the UK, the RSPB has over a million members, while in the US where it is estimated there may be as many as 70 million birdwatchers, the Audubon Society has numerous centres in every state). There are holiday companies that specialise in birdwatching and trade fairs dedicated to all those with an ornithological leaning. The birdwatcher’s image has changed, too, and it is a great pleasure now to see people from all walks of life watching birds.

So why are birds so popular?

To claim that they are easy to get to know is inaccurate – they can be some of the most frustrating animals on the planet to study. But as a group they are active and conspicuous, which makes them appealingly accessible. In almost any city in the world you can look out of your window and see a bird. Many are fabulous to look at and have a deep aesthetic appeal; they can also be capable of extraordinary feats of migration and some fascinatingly diverse habits and survival strategies.

Feathers are the most obvious thing that separates the birds from all other living things. These versatile, disposable, flexible, insulating, lightweight, easily maintained, interlocking, ‘scale-like’ structures are unique to the birds.

They are also the secret to their success, as bats are the only other masters of true flight, and feathers really do have the edge over the patagium (that flexible thin skin that is the wing of a bat). For a start, if feathers are damaged they can be regrown, which the patagium cannot, and feathers mean that birds don’t have to have long, thin, fragile bones, and so their wings are much more robust than a bat’s. Feathers make great insulation, which is why birds can maintain their body temperature more efficiently than any mammal – and why we make duvets out of them. A bat’s wings, on the other hand, act like giant radiators, which limits where they can live and when they can be active. The fact that a bird’s wings (unlike the front limbs of a mammal) are independent of its legs also means that all the other diverse uses to which it puts its feet, such as grasping, preening and manipulating, have been honed to perfection.

As a boy I was obsessed with feathers. Even today, while I do not go to quite the same lengths to obtain them (I once suspended my unfortunate younger brother by his legs into the Ostrich pen at a local zoo to procure a fine fluffy specimen for me), I still cannot help but bend down and pick them up whenever I see them. Not only are they the most perfectly beautiful example of form and function in the natural world, but many also come in fabulous colours, and for the expert naturalist, every feather tells a tale.

Feathers are made of a flexible protein called keratin, the same stuff as human hair and nails. The reason they are so light for the area they cover is that the shafts are hollow. All the other parts are made up of tiny interlocking strips called barbs, ‘zipped’ together by little hooks called barbules. If you run your finger backwards along a flight feather, you mess it up, because you have ‘unzipped’ the barbules. This happens to a lesser extent during everyday wear and tear. If you smooth your finger back up the feather you cause the barbules to ‘zip up’ again, which is exactly what a bird is doing when it preens itself. Despite their proverbial lightness, feathers make up nearly a quarter of a bird’s total weight. They can actually be heavier than its skeleton!

To a naturalist the feather is much more than a bit of windblown fluff; it can tell an awful lot about the previous owner. Different feathers on a bird’s body grow from distinct places, or tracts, known as pterylae. When fully developed these feathers take on their own distinctive shape and appearance, and with a little practice, you can identify these.

Super sleuth

The next level of expertise is to be able to identify the difference not only between species but also between sexes, ages and moults. I have a friend who works on prey selection of certain species of raptor such as the Peregrine Falcon (Falco peregrinus), and because these birds are messy eaters, if you can retrieve the feathers and meal remains, you can construct a fairly good idea of the bird’s menu. Sometimes these dinner remains throw up some real surprises, like new records for species of bird in the area.

The growth and renewal of feathers, known as a moult, is controlled by hormones and is a fairly energy-expensive operation, requiring a lot of effort and a reduction in efficiency, and so moulting periods are synchronised with other major events in the bird’s annual life cycle, such as breeding and migration. An example of this occurs on the predator-free mudflats of the Severn Estuary where in the late summer, after breeding, Shelducks (Tadorna tadorna) congregate to moult. This mass moulting is so spectacular that the first time I witnessed it, I thought I was looking at an unseasonable fall of snow – there were literally millions of feathers blowing around in drifts on the muddy shore. Shelducks and other waterfowl become very vulnerable at this stage as their powers of flight are often totally compromised, and so some enter ‘eclipse’ plumage, becoming very dowdy in appearance to avoid unwanted attention from predatory eyes.

Most birds moult completely two or three times every year for a variety of reasons other than simply to renew the feathers. Some moult into gaudier plumage prior to breeding to display to potential mates. But to continue this beyond the breeding season would only advertise yourself to predators, and so a second moult restores the bird’s previous low profile. In other species, feather wear has evolved to occur at a certain pace. The European House Sparrow (Passer domesticus), Starling (Sturnus vulgaris) and Chaffinch (Fringilla coelebs), for instance, all seem to change colour and brightness as winter turns into spring. In reality they do not moult at all – the feather fringes simply wear off and create the illusion of a brighter bird.

Despite spending a lot of their time above the ground, birds leave a surprising amount of evidence on the ground in the form of nests, feathers and egg fragments. And when they do finally come to earth, they leave tracks. It is a little harder than with mammals to identify individual species by these alone, but once again, combine the physical clues in the footprints and field signs with other information such as the distribution and knowledge of an animal’s habitat use, and you can start making good guesses.

To help you narrow down your choices and obtain a positive identification, bird tracks can be divided into three main categories. None of these is linked to phylogenetic relationships; the tracks just coincidentally show a number of shared features.

Ground birds, waterfowl, waders and shorebirds include game birds such as grouse and pheasants, waders such as sandpipers, cranes, gulls and waterfowl such as ducks and geese. All these birds have three toes pointing forwards and one short one pointing backwards. The pattern of the toes tends to be symmetrical. With ducks, geese and gulls, the rearward pointing toe doesn’t always register, while with game birds, if it registers, it is as a nail hole. Webbing between the toes of gulls, ducks and geese will show on a soft substrate such as mud and can give you a big clue to the treader’s identity, but it doesn’t always show up. So always check the shape of the two side toes – if they curve inwards, the track belongs to a web-footed bird.

Perching birds, herons and ibis make up a huge category that includes pretty much every bird capable of gripping a branch – songbirds, birds of prey (excluding owls), pigeons and crows among them. This category encompasses many sizes and lifestyles, and as a result there is large variation in size and a degree of asymmetry between the forward-pointing toes. But the big distinction is that the rear-pointing toe is often nearly as long, if not as long, as the toes pointing forward. Because of their raptorial purpose, a hawk’s toes need to be sturdy and well constructed, which is reflected in its footprints.

Woodpeckers, cuckoos, owls, parrots and roadrunners often have two toes pointing backwards or certainly not forwards, giving a rough ‘x’ or ‘k’ shape.

You can also glean a limited amount of information about the bird’s gait from its footprints. Stride length can give you an idea of leg length, and a walking bird will leave an alternating pattern while a hopping bird leaves pairs of tracks next to each other. Shelduck footprints resemble those of any similar-sized waterfowl, but because this bird has a characteristic method of feeding, with a repetitive sideways sweeping of the bill, it leaves a trail of horseshoe-shaped beak tracks as it walks. Dunlin (Calidris alpina) work their way across the mud, randomly probing with their bills and leaving a trail of single holes like stitch marks. Snipe (Gallinago gallinago), on the other hand, probe with their bills held open, leaving paired ‘double stitch marks’.

Eggshells often turn up on lawns, or you may stumble upon them out in the field, especially in the spring. The big question is, did it hatch naturally or was it predated? When a chick hatches naturally, it chips away at the shell using its ‘egg tooth’ and usually makes a neat job near the blunt end. The papery membrane within the egg is preserved and its edge protrudes outside the shell, often curling inward when it dries. The inside of the shell will also be clean. The presence of eggshell doesn’t mean there is a nest nearby: once the chicks have hatched the adult often dumps the shells far away so as not to attract predators. A complete egg, particularly if it is pale blue, can be explained by the behaviour of Starlings: one will often nip into another Starling’s nest, lay an egg of her own and remove one of the original clutch.

A predated egg, on the other hand, is clearly a predated egg. Whether the egg thief is a bird or a mammal, the job is usually messy; the shell may be split into more than two pieces or simply have a small hole in it; there may also be remains of yolk, egg white or blood (if the embryo was well developed). If the predator was a mammal, the shell may bear witness to this by showing the punctures made by canine teeth. The distance between the marks can also hint at the identity of the predator. The best clue, though, is that the membrane in a predated egg rarely projects beyond the edge of the shell.

The shells of ground-nesting birds such as ducks, gulls and game birds often remain in the nest after hatching. Their remains may be found crushed in the nest or abandoned as the chicks are frog-marched out of the area by the parent birds. A nest like this is worth closer inspection, as it may have been raided (whole clutches can be consumed by predators) and you can use your detecting skills to deduce what has happened.

We’ll talk a lot more about excrement in the Mammals chapter, and some of that information applies to birds too. But birds of prey do it differently. They excrete only liquid waste from their vent; their solid matter comes back up the way it came in.

The non-digestible portions of a bird’s diet that never make it through the system are regurgitated back up the gullet in the form of a pellet, or cast. Owls are famous pellet-producing birds, but all raptors and members of the heron (Ardeidae), crow (Corvidae) and gull (Laridae) families at some time or another eject these nuggets of indigestible stuff. In the absence of any other evidence, it can be hard to tell which species produced which pellet. But there are a few guidelines that can help you sort this out, starting with the most frequently encountered pellets, those of owls and hawks.

Hawks have much stronger digestive processes than owls and a different way of feeding – they generally tear and pull the flesh from the bone. This means their casts are of a finer texture. All but the biggest bone fragments are dissolved, and in most cases, just the fur and feather fibres make up the bulk.

An owl’s pellets tend to be much coarser and fibrous as most of their diet consists of smaller prey items that are entirely consumed and sometimes even swallowed whole. Therefore the pellets tend to be more revealing about its diet, and pellet analysis is not only a major part of owl dietary study in its own right, but also a very important way of monitoring the populations of small mammals in an area. These in turn can be sensitive indicators of environmental variations such as land-use change or the arrival of an introduced species.

Finding pellets

The best way to discover these revealing deposits, especially in the case of hawks and owls, is to locate roosts. Owls tend to return to the same places to roost in disused farm buildings, outhouses, tree cavities and even large parkland trees. They may also make themselves new more caption prominent barn owl by pellets being ‘whitewashed’ by the birds’ liquid waste. Hawks also have favourite roost sites, be they fence posts or old trees, and these are your best bet, though the pellets are harder to find as they are produced and ‘lost’ as the bird goes about its wide-ranging daily business.

With other pellet-producing birds, look around nest sites or under rookeries and heronries. Gull pellets are a common find anywhere on the coast, particularly among tussocky hummocks on cliff tops, but they can turn up pretty much anywhere a gull has stopped. Being scavengers, the contents of gull pellets tend to be very varied and interesting – you can find anything from foil and string to more natural and expected dietary items such as fish bones.

Pull apart an owl pellet, and you will find all manner of bones, not just the big and bulky ones, but also complete skulls of small mammals, small birds, even frogs and lizards. Before embarking on this record the appearance and weight of your pellet.

Carefully break the pellet into chunks and soak in warm soapy water for a few hours. Tease them out and gently stir or agitate the solution. The heavy stuff such as bones and teeth will sink to the bottom, allowing you to decant and tip away the lighter debris such as fur and feathers. Use a sieve in case you overpour and lose some of the bones, which can be picked up with forceps and returned to the pot. Repeat this process several times until only the bones remain. Transfer them to a shallow dish and sort through them with cocktail sticks or dissecting needles. Use a fine paintbrush to remove any remaining traces of softer tissue.

Once you have extracted the bones from the pellet, you can, if you like, bleach them (see here). Do not leave bones this size in the bleaching solution for long, as they will become even more fragile and the teeth have a tendency to fall out. Display and store your collection of fiddly fragments by gluing them to a piece of black cardboard, and then add the written notes you took before you started.

Do not mistake simply looking at and identifying birds as birdwatching; for me it means much more – observing their behaviour and learning about their lives and how they interact and work to survive. For example, you might identify eight species among a bunch of waders tottering around on estuary mud, but the true birdwatcher will see how they are spaced out so as not to interfere with each other’s easily disturbed prey items; notice that the plovers are involved in a feeding sequence – look, dash, look, peck – while a dunlin randomly stitches its way across the mud. You might even notice three different feeding strategies employed by one species of Oystercatcher!

That is the detail, the fascination of birdwatching. The identity thing, though important, becomes second nature, especially on your home patch. On paper, trying to describe a pigeon and a Peregrine Falcon flying is very much the same, but as soon as you gain experience you will almost instinctively pick up on the GISS of a bird. Though this is often written as ‘jizz’, it is really an acronym for General Impression Size and Shape and refers to the quick summary, or ‘feel’, that allows you to identify a species at a glance.

Most birds produce a rich range of sounds. Mostly uttered by the bird’s syrinx (voice box), these are not just loud, proud territorial claims made mainly by males during the breeding season; the repertoire also includes a complicated array of more subtle avian small talk that is used all year round simply to communicate. There are alarm calls, songs, subsongs, whispered songs, begging calls and contact calls to take into consideration. Some birds also produce sounds other than calls: the ‘drumming’ display of snipe over a sodden grassland, the irritated ‘clack’ of an owl’s bill or the percussive drumroll of a woodpecker are good examples.

When I started going out on dawn-chorus walks, I was invariably surrounded by people who really knew their stuff. At first I was inspired by the ability of these superior beings to distinguish the subsong of a Blackcap (Sylvia atricapilla) from all the other subsongs of a bunch of newly arrived warblers, but soon it became daunting. I retreated into my ignorance and stopped asking questions before slinking off to cry into the pages of my field guide.

It took me years to recover, but here is how I did it. I finally realised that these knowledgeable people were not in possession of a divine gift but had actually learnt their skill over time. And that is the key: it takes time. Seeing with your ears is a two-part process. First you have to hear the bird, then you have to make the connection between the noise and the vision. You need to get to the stage where the sound of a song or call instantly takes you back to the moment you first saw it being created. It is a matter of basic association in the same way as a certain piece of music can act as a shortcut to memories of your first kiss or your first pair of binoculars (is he joking, you have to ask yourself?). Collecting these experiences really does boil down to time taken in the field – the more you look, the better you get. Having said that, there are a few ‘tricks’ that can help you get there faster.

1. Make life easier for yourself: start by working with a few familiar species in your neighbourhood. Get to know their repertoire and move on to other species as you become familiar with those that create the local ‘audio wallpaper’. In temperate climes, the best time to do this is at the beginning of the year before all the migrants arrive and confuse things. Teach yourself to listen and hear each voice, then, using all the skills of stealth and patience so key to a naturalist’s activities, persist in trying to see and identify the bird making the sound. To home in on different calls and the direction they are coming from, try cupping your hands behind your ears and moving your head about.

2. Sound associations: many bird calls are very distinctive, but to help you remember them, there are various phonetic renderings that can be applied. In Europe the song of the Yellowhammer (Emberiza citrinella) can be heard, with a little poetic licence, as ‘a little bit of bread and no cheese’, the Quail (Coturnix coturnix) as ‘wet my lips’. With others just the cadence or the sounds can be likened to familiar things: Bobolinks (Dolichonyx oryzivorus) have been described as R2D2 shorting out; the common song of the European Chaffinch allegedly has the pace of the footsteps of a fast bowler winding up to bowl; and the Wood Warbler (Phylloscopus sibilatrix) sounds like a coin spinning.

3. Expand on the above: mnemonic phrases – those little descriptions you often see in field guides that write the sounds of bird songs and calls as collections of letters – can help once you are at a certain stage of expertise. It is also a neat little trick to draw these sounds! That may seem odd, but when I think of a sound, I often make a mental picture of it. Try drawing things like a wavy line for a rising and falling song, a broken line for short, staccato sounds or an upward curve for a short call that starts low and ends high. This is a technique and a language that will be distinct to you.

4. Keep testing yourself: nobody knows everything; even an experienced birder on his or her own patch will sometimes hear unfamiliar sounds. Never become complacent. Hear a bird, identify it in your head, then go and see if you can catch sight of it and find out if you guessed right. No matter how experienced you are, this is a good way of staying sharp. I often have to relearn the songs of all the migrants that, in the UK, sing only for a month or so every springtime.

5. Use sound references: in the same way as you may use a reference book on your return from the field to help interpret your observation, you can do the same with bird songs and calls. There are a large number of CDs, DVDs, ebooks and Apps that act as audio field guides, helping you to reach positive identifications or remove any niggling doubts about the sounds you have heard.

Listen for the difference

Almost impossible to tell apart without a good view, Marsh (above) and Willow Tit are easily identified by their different voices.

A noise can be thought of as an audio fingerprint to a species, and it is often easier to make a positive identification of a bird by its call than by its appearance. Take, for instance, the Marsh Tit (Parus palustris) and the closely related Willow Tit (Parus montanus) – two birds that, even when you have one in each of your hands, still confound many of us! But listen to them call, and you will be in no doubt – if it’s sneezy and wheezy, it’s a Marsh Tit; if it’s more aggressive and scolding, it’s a Willow.

The breeding season, particularly the spring for temperate species, is a time for birds to do battle – not with beak and claw but with their voices. Common garden birds are setting up their territories and defending them against their neighbours by shouting all about it.

Now is the perfect time for you to map the territories of the birds in your patch. Simply get up early and look for males singing – they usually choose high perches in the centre of their kingdoms, overlooking as much of their territories as possible. Jot the positions on a map (using different colours for different birds), watch where they fly and try to shadow them, but do not worry if you lose track – you can pick up where you left off the next day. If you see two male birds close to each other, you can assume that each is on the boundary of his territory. Over a few weeks you will start to notice the invisible lines that are the territorial boundaries within which most birds move. Soon you will not only have a unique record of the movements of the birds in your neighbourhood, you will also become a top bird spotter and learn a lot about bird song. If you supply a variety of nesting materials such as bunches of animal hair, wool, string, fluff and even a shallow dish of mud, it won’t be long before the locals start visiting; by watching which way they fly off with their beaks full, you can often work out the locations of their nests, too.

Another famous territory exercise is one that should be tried only occasionally. If you repeat it, you will cause the birds a lot of disruption, stress and wasted energy. But it works particularly well with the European Robin and is worth doing once to observe the ferocity of these seemingly harmless little songsters. Just as a male Stickleback responds to the stimulus of a red model fish (see here), so the male Robin will attack a model Robin (it doesn’t even have to look realistic, just have a red breast) with a fury and boldness that will surprise all who witness it!

This technique is not restricted to birds, and much of the following advice can be used to record pretty much any animal vocalisation. As so often, the better the equipment, the more expensive it will be, but to start with cheapish recording gear is fine; you can even make reasonable recordings on your smartphone, especially if you get your hands on a plug-in mic. Essentially you need two bits of kit: a microphone to turn sound into an electrical signal and a recorder to capture and store this information.

Microphones: the biggest obstacle for anyone trying to record wildlife sound (especially bird song) is distance; just halving the distance between you and your subject increases the power of the recording by a factor of four. This problem can be overcome in many cunning ways, such as leaving microphones next to singing posts. But the easiest way around it is a decent microphone. You can think of the microphone as being analogous to the lens of a camera or a pair of binoculars. As with optics it pays for go for quality. To ‘catch’ a song and minimise background noise, you really need directional microphones (mics designed to record human voices are not as suitable as those used for recording music) or a dish-shaped device called a parabolic reflector, or parabola. Parabolas come in a variety of sizes – the larger the dish, the more the sound is amplified. But it is worth noting that low-frequency sounds such as those uttered by owls and pigeons do not record well if the diameter of the dish is less than the wavelength of the sound – the recording may sound a bit weak and watery as a result. It’s a compromise between size and practicality; a dish can be a handful moving through dense undergrowth or in strong winds. Around 50cm (20in) in diameter is pretty good for most purposes.

Recorders: the requirements here are simple. Recorders need to be portable – that reads as lightweight – strong, robust and reliable. HiMD Minidisc recorders are good value options, but there is so much to be said for getting the latest solid state recorders – they have less to break. They are, however, quite expensive. The advantage is that they record at what is called a higher bit rate (the best way of understanding this is that it is equivalent to the megapixels of a digital camera) which means more sound information is recorded. The best bet is to start with what you can afford and read up on the various specialised websites before investing in better equipment if the bug takes you.

It’s hard being a human when all you want to do is get close to birds and all they want to do is ‘vote with their wings’ at the slightest perception of a threat. Fortunately there are ways of tricking them into showing their beaks. Become a bird impressionist and you can sometimes ‘call them in’ so that you can have a closer look.

Interfering with wild birds in this way is controversial and while it was something I would do regularly as a young boy, nowadays the technique is much more widespread, especially with the advent of the smartphone. I’m including this for completeness, but urge any young naturalist to think first and put the welfare of the birds first.

The most universal technique, which works well with lots of small passerine birds throughout the world, is a stylised form of alarm call known as ‘pishing’, producing by blowing air sharply over your tongue while it is squashed between the roof of your mouth and your lower teeth. The noise you are aiming for is a kind of ‘pursheeee”.

It works best in a sequence of three, repeated at intervals. The birds hear you sounding the alarm and come to see what predator they have missed – behaviour you may have seen when small birds ‘mob’ magpies, crows, owls and raptors.

When ‘pishing’ fails, try chipping – a short, sharp, kissing noise between tight lips. This is sometimes enough to make the birds appear, if briefly, out in the open.

When birds are flying overhead and you have no time to reach for your binoculars, try a short ‘pew-pew’ or a single loud ‘pish’; these calls are sometimes enough to cause the flyer to plummet out of the sky to avoid the imaginary predator that you have just warned it of.

‘Calling in’ by squeaking works equally well for predators such as Foxes, Stoats and Barn Owls.

You may think that, being nocturnal, well-camouflaged, woodland birds, owls would be pretty well impossible to see. But Europe’s Tawny Owl is fairly ‘birder friendly’ as owls go. It is an adaptable bird and, although principally a woodland species, it is tolerant of human disturbance and the only owl to have populations in our cities – in fact, some of my best owling moments have taken place in a car park, watching a Tawny hunt young rats foraging around a litter bin from the vantage point of a No Parking sign.

Calling them in works best in the autumn and winter. For a start the leaves are falling, allowing better views. But also at this time of year there is a lot of shouting in the owl world after dark – the young have been ousted from the territories in which they were raised, and they and other birds are competing for territories that must not only supply food through the coming winter but also have suitable resources such as roosts and nest holes for the late-winter breeding season.

Blowing between your thumbs into an airtight cavity produced by your cupped hands generates a Tawny Owl impression that, though not a patch on the real thing, is often enough to start the blood of a resident male boiling. Do this near where you hear owls calling, and with the use of a torch, you are almost guaranteed to see an owl. At close quarters you will also appreciate that cliché sound of the night, not as the well-known and over-simplified ‘hoo-hoo-hooo’, but as a throaty affair with wavers and croaks. Play fair, though – once you have set eyes on your bird, stop the impressions and let the owl go back to its business undisturbed.

Probably the most bizarre method is that used to attract the European Nightjar (Caprimulgus europaeus) in spring when the birds have just arrived back on their heathland breeding grounds and are setting up territories. If you approach a site at dusk, just as the birds are getting up for the night, and wave white handkerchiefs in the air whilst clapping your hands together like a morris dancer, you may well lure in a testosterone-laden male bird, also flashing his white wing patches and clapping them together in a bid to challenge you.

This last trick can be much improved (and I have had a nightjar think about perching on my head while I was doing this) by playing a recording of its own call back through speakers; this is known as ‘tape luring’. This way you do not even have to attempt to impersonate the bird, and nearly every time I have tried this I have had success. Not just with nightjars, either – many other species are attracted to their own voices.

Nightjars generally use their far-carrying frog-like call only in the mating season. Males also clap their wings together as part of the courtship ritual or to warn off rival males. But note that Nightjars are a Schedule One species and as such are protected by the law, so disturbing them at the nest is a serious offence.

Code of practice

On the face of it, it may seem fun impersonating or tape-luring a bird, but it’s worth considering the fact that you are at best inevitably distracting it from its activities, at worst you are distressing it and other birds in the neighbourhood, and if it is by a nest, the alarmed activity can easily draw the attention of a predator. It is undoubtedly a useful technique among scientists and bird surveyors and while a magical experience can no doubt be generated and a difficult bird might be seen it is worth bearing in mind some codes of conduct. The advent of the same smartphone apps that help us learn bird song has also led to an increased use of tape luring. Normally if bird calls or song are played for a very short time minimal disturbance is caused. But in heavily birded areas such as nature reserves, or with rare and sensitive species, it is generally considered bad practice; also these stressed responses whether territorial or predatory use energy that birds do not always have to spare. While the science is a little confused, common sense should really prevail; if we were talking about individuals occasionally using the technique – then it’s not really a problem, but when you’ve got a large number of birdwatchers visiting a small site or a tiny population and they are all doing the same thing to get a view of the bird, then this is a bit more serious.

I prefer to subscribe to the school of using your field skills to get you a view of the bird behaving naturally. In many countries disturbing birds at the nest is illegal even for common species – in some instances using call playback and tape luring is considered disturbance and to do it you would be breaking the law.

When you feed birds in the park or put up a nestbox for them in your back yard, you are providing a necessary resource. This is a good thing and it is even better because it’s not a one-way relationship; it makes you feel good for helping out and if you’re clever in how and where you position your feeders or nesting boxes you can improve your views and enhance your understanding of their fascinating lives. There are many books and websites dedicated to this vast subject, so once again what I will do here is point you in the right direction and suggest a few of the cheaper and more eco-friendly ways of achieving the desired results.

Feeding first: there is a battery of different feeders available to dispense seeds, nuts, kitchen scraps, suet-based recipes and water to your birds; they vary in design from a piece of board to a top-of-the-range, squirrel-proof affair that comes as part of a huge and burgeoning market in purpose-built, designer bird feeders.

With some inventiveness tins of the kind coffee and baby food come in can be turned into seed feeders by drilling three holes in the sides close to the bottom, then one through the centre of the base. Align this with a hole in a plastic saucer or drip tray, then either screw the whole thing onto a post or suspend it and fill it with seed.

You can make a feeder at home or you can spend as much as you like to attract these animals close up.

Bird cake or pudding, made from warmed suet mixed with any variety of seeds, fruits, nuts or insects and left to set, can be served up in many ways. Put it in a tin wedged in place between three blocks screwed to your bird table, hang it in pots, cartons or half coconuts, or jam it into large holes drilled in logs – a favourite for woodpeckers.

You can make your own seed feeder from those horrible plastic milk bottles that seem to have taken over the supermarket shelves recently. I recommend the 1 litre (2 pints) or larger sizes, unless you do not mind refilling them twice a day.

•twigs or any straight bits of wood, and string or wire to attach them to branches

1 Draw a line on the bottle 1.5cm (½in) from the bottom on the side opposite the handle, parallel to the base, and cut carefully along it. At each end of the incision, cut up about 3cm (1in).

2 Fold the flap you have just created back into the bottle and, hey presto, the bottom of the bottle becomes a feeding tray.

3 Make a couple of perches from the wood and stick them into holes below the feeding tray.

These are the wriggly larvae of beetles and can be bought in many pet shops, especially those that deal with reptiles and amphibians. There are many mail-order stockists, too, and so a fresh tub will turn up every Wednesday if you so desire. Mealworms can raised in the airing cupboard – keep them in a well-ventilated box with a tight-fitting lid and feed them on oatmeal, bread, biscuits and the like.

A handful of wriggling mealworms may not seem very appetising to you, but Robins find then irresistible. Start by putting a small margarine tub with a few mealworms in it on your lawn to get your local Robin interested. As the days go by, stand out in the garden while it is feeding, inching closer every day. Different Robins have different tolerance levels. So there are no rules about how long getting to within arm’s length will take. Just be patient. Keeping low or even lying down may help. Now comes the hard bit – making contact. Offer the mealworm in the same tub, but hold the tub in your outstretched hand. If your Robin is at the right stage of conditioning, it should feed fairly happily. Let him or her settle in to this pattern for a few days, then when he or she seems relaxed, remove the tub and place the worms in your palm. And you should have a hand-tame Robin!

If at any stage you fail, go back a step and keep trying – it is worth it both for the robin, who gets vital food of the right kind, and for you, who will get the rare thrill of contact with a wild bird.

Feeding mealworms to birds can be tricky as they have a tendency to crawl off, something a peanut cannot do. This can be overcome by serving them up in containers with a high enough edge to stop them escaping. Watch for rain, though; drill a drainage hole in the bottom to stop your worms drowning – if they are dead, they stop wriggling and soon go mouldy.

Beware of cheap imitations

When buying mealworms, do not be tempted by cheaper imitations – to the uninitiated, there may not be much difference between maggots and mealworms, but remember that maggots are commercially grown for fishing and may contain chemicals; also they have been brought up on dead-animal material and may contain contaminants that are bad for your birds. Mealworms, being vegetarian, are much more like the caterpillars and grubs that birds feed on in the wild.

Be patient. If you have just started feeding the birds in your garden, it may take them a while to learn about your service and add you to their daily rounds.

Keep areas under feeders clean. If they are positioned over hard standing, sweep and disinfect it regularly; wash and scrub down your feeding devices as well. Feeding stations, with their high numbers of visitors, are perfect places for disease transfer. Plus the tidier your feeders are, the less likely you are to attract unwanted guests such as rats (though if mammals are your thing, this may be a bonus!).

Use good-quality foods, ideally from a purveyor of seeds and the like aimed at garden birds. Many of the selections you see in the bargain basement have a high concentration of wheat (not a problem if you want to feed pigeons, pheasants and chickens, but not attractive for smaller birds). Peanuts that have been badly stored may contain a fungus called aflatoxin that is lethal to small birds. So buy wisely.

Choose a variety of foods. Not all birds like eating the same things: hummingbirds have specialist requirements and need a sugary liquid; finches go for seeds such as niger and sunflower; tits are crazy about nuts; thrushes like fruit; and woodpeckers love fatty, suet-based stuff. Provide water nearby, so that the birds can drink and wash between meals. This is especially important in the winter if temperatures fall below freezing. Keep the ice away by placing hand warmers or candles below a metal dish of water, regularly pouring in hot water from the kettle, floating a ball in the water or splashing the cash on a heated bird bath (yes, they really do exist).

Provide a varied menu and you’ll get a variety of bird species – Chaffinches (left) are seed eaters and relish a variety of seeds, while Siskins (right) have a finer beak and go crazy for the fiddly little niger seeds. Robins and thrushes have a leaning toward insects – mealworms are a favourite.

Put your feeders in an open location but with cover nearby. This means that next door’s cat cannot sneak up unawares, but the birds will feel secure knowing there is natural cover into which to dive if a predator such as a hawk shows up. Feed in various locations. Some birds are bold, others shy, so by all means provide food close to the house, but don’t forget the nervous ones – put a little at the end of the garden, too. Also bear in mind that different birds feed in different ways; some rarely get onto the bird table but prefer to stay on the ground; others like flat surfaces; some like to hang.

There is a myth that you must stop feeding the birds in the summer/breeding months. This is just not true, as birds are more pressed than ever to meet the demands of their nestlings. What you should do, however, is avoid large food items such as peanuts or bread crusts that can be removed whole, as these, when fed to nestlings, may cause them to choke and die. In summer keep the food small and soft.

Dependent feeders. Many people worry that the birds in their garden may become so dependent on their feeding that, when they go away, the birds will starve. Well, don’t feel you have to cancel your holidays. It is thought that many garden birds treat feeding stations as they do patchy food resources in the wild: as soon as food dries up, they move on to somewhere else in the neighbourhood.

Don’t be afraid to experiment. Rather than putting nuts in feeders and crumbs on the lawn, attract a few more finches by collecting teasel seedheads and sprinkling tiny black niger seeds into the natural seed chambers. This makes the seedheads recyclable, whereas in the wild they would be used only once. Try melting fats into some of the seedheads – Blue Tits love it. Alternatively, drill holes in a log, fill them with suet and you have the perfect woodpecker feeder.

Bird cake or pudding: this animal-fat-based food made from warmed suet mixed with any variety of seeds, fruits, nuts or insects and left to set can be served up in many ways. You can provide it in a tin that is simply wedged in place between three blocks screwed to your bird table, it can be hung in pots and cartons as well as half coconuts or jammed into large holes drilled in logs – a favourite for woodpeckers.

A variation on the theme

As well as putting food out for the birds during the winter, how about putting nesting materials out in the spring? When out walking, collect tufts of sheep’s wool caught on barbed-wire fences, horses’ hair, feathers, dry grass and hay. Add long hairs from the hairbrush and the fluff from the Hoover bag, bundle it up, hang it around the garden or on the bird table and see who comes and takes what for their nests.

The birdbox has been a feature of many gardens for some time, but with the continual squeeze on wild bird nesting places in many parts of the world, due to urban development and drastic changes in land management and farming practice, the back garden is becoming an important sanctuary.

Lack of suitable nest sites holds many bird populations back, and providing them is one way that the amateur naturalist can plough back a little. This is a two-way relationship – you give them nestboxes; in return you get a focus for your studies – and with a bit of techno wizardry, you can elevate the humble tit-box to new heights.

Having birds use a box in your garden allows you to become familiar with intimate goings-on that would usually be hidden in the tangles of the wild. One rather frosty evening, I watched a Wren enter an old nestbox hanging on my garden wall. I was surprised, as up till then no bird had ever condescended to use my home-made box in the breeding season, but I watched with interest, thinking he might be hunting for spiders. Fifteen minutes later, without having noticed him leave, I saw him go in again. After the fifth sighting, I got suspicious and stayed with my eyes glued to the box hole. It soon became apparent that, unless my box had sprung a leak, there were many birds sheltering there; by the time dusk had fallen I had counted 23 Wrens.

Since then I have done a bit of homework and discovered that the record is 61 Wrens in a standard Blue Tit box – the ornithological equivalent of cramming students into a phone box, I guess. The explanation is that the birds are effectively creating one superwren, huddling together and reducing the surface area through which they lose body heat.

Come the beginning of spring, as the birds begin to start calling and warming up for breeding, you will see them beginning to inspect cavities and eventually taking up residence. The real action starts when the eggs inside hatch and the parents’ comings and goings increase in response to the demand for food. Just counting these visits and noting the sort of prey they bring in is the key to a much greater understanding of even our most common birds.

Nestboxes are not all boxlike – they can be anything from the classic cavity box with a hole to the very latest in woodcrete architecture (a secret combination of wood and concrete that is supposed to have insulating properties and allow the cavity to breathe). They can be a floating raft for Moorhens or a floating beach for terns, a construction the size of a tea chest for owls or a little woven reed or rope ball for Bearded Tits (Panurus biarmicus); and these are just those intended for nesting. Birds can also be surprisingly good at improvising – every year I hear of a selection of bizarre nest sites that has included overcoat pockets, car exhaust pipes, crash helmets and even a human skull.

The following are a few ideas to be getting on with, but as usual be creative, check out some of the books recommended at the back of this one, and you are sure to come up with a desirable residence for the birds in your garden.

This is the most common form, attractive to a whole host of small birds. A hole with a maximum diameter of 32mm (1⅛in) is good for most tits, Tree Sparrows and Nuthatches.

•a plank of wood about 15cm (6in) wide, 122.5cm (50in) long and 1.8cm (¾in) deep

1 Working on a solid surface such as a DIY workbench, saw a 45cm (18in) length of wood off the plank. Cut this again on the diagonal so that you have two identical pieces, each with one long side measuring 25cm (10in) and the other 20cm (8in). These will make the sides of your box.

2 Drill a hole near the top of the piece that will be the front. (Its size will depend on the size of the bird you want to attract – see here.)

3 Cut the remaining length of plank into four pieces, measuring: 25cm (10in) long for the back; 20cm (8in) for the front; 21.5cm (8½in) for the top; and 11cm (4½in) for the floor.

4 Screw, nail or glue the back to the batten, which should stick out a bit at both top and bottom. Then fix the rest of the box together with the longer ends of each side towards the back. Leave the roof till last and fix it on with the hinge. Try to avoid any gaps and you must drill a few holes in the bottom for drainage and ventilation.

5 Nail through the top and bottom of the batten to fix your box to a tree or wall, high enough to be safe from cats and other predators. See here for advice on positioning.

If you want to attract Robins, Wagtails and Spotted Flycatchers, make an open-fronted box using the dimensions given above, but with the front piece only about 7.5cm (3in) high. Nail it to a tree or wall in a sheltered spot and partially cover it with climbing plants. Adding a handful of straw or similar material will make it even more attractive. An open-fronted box about twice this size may lure Kestrels, Sparrowhawks or Little Owls.

Treecreepers will visit a box that mimics their preferred natural nesting sites – a crevice in a tree or under a piece of loose bark. Cut two rectangular pieces of wood about 16.5cm (6½in) by 30.5cm (12 in) and two triangular pieces with two sides measuring 16.5cm (6½in) and the other 23.5cm (9¼in). Cut a semi-circular notch about 2.5cm (1in) in diameter out of one long side of each of the rectangles, about 5cm (2in) from the end. Nail the two rectangles together at an angle as shown, with the notches on the outside and near the top, then add the triangular pieces to make a roof and a base. Use mirror plates at the top and bottom to fix it all to a tree, which forms the back of the box, and glue a few strips of bark to the outside so that it blends in with its background.

If a swift can’t find a suitable roof to nest in – quite likely if your area consists of predominantly new houses – it will appreciate a special birdbox. The correct designs for a swift box can be found at www.swift-conservation.org.

Fix the box at least 6m (20ft) off the ground, preferably at roof level, under the eaves, and be patient – it may take the swifts a few years to move in.

Thanks to technology continuing to make everything smaller and cheaper, it is now possible to buy reasonably priced kits that allow you to view the most secret lives of birds in your nestboxes. A kit consists of a very small infra-red camera with a length of lead that simply plugs into the back of your computer, video or TV. So when there is nothing on the telly except reruns of Friends, you can flick over to see what the tits are doing.

The cameras are intended to be fixed into the roof of the nestbox and with some of them you don’t even have to do this yourself – the kit comes with its own box. All you have to do is nail it up and plug in, and the birds will do the rest. The lenses are fixed, but because the field of view is so wide, the entire contents of the nestbox will be in focus. With the camera high up in the box, the lens remains fairly clean and splatter-free, though when the nestlings start getting cabin fever and realise what their wings are for, the dust does begin to fly. Any muck that gets on the lens can be quickly polished off while mum and dad are away. When your nestlings have moved off, keep watching, because the parents may try for a second family or another pair may move in. If it all goes quiet, you can simply reposition the camera, perhaps in a hedgehog box or on the mammal table.

Once you start ‘bugging’ your box like this, there is no limit to the possibilities – colour pictures, night vision, microphones, light sensors that allow internal lights to come on and go off. And why limit yourself to the inside of a box? Why not try some of the waterproof units that will allow you CCTV coverage of pretty much every inch of your estate?

‘Location, location, location’: positioning the box

You can have the most fabulous, comfortable, centrally heated ‘des res’ with mealworms on tap, but if it is sited incorrectly, it will house nothing but the beetles you placed in there in the first place. The positioning of your birdboxes is critical; different species have different requirements such as height and relative positioning to other garden features. Robins and Spotted Flycatchers (Muscicapa striata) seem to prefer more open boxes than tits, and sparrows like theirs close to thick bushes; they also choose their nest sites early in the season, and so in the northern hemisphere, put your box up by Christmas if you want to attract sparrows.

The two most important things to take into consideration are shelter from inclement weather, not just rain and wind, but extremes of temperature, too; and safety from predators such as cats. These needs then have to be balanced with your own – how viewable you wish the boxes to be and how easy they are to clean and service (by this I mean an annual scraping out of debris and any necessary external repairs). The time to do any maintenance is during the winter months; this is also the season to reposition the boxes if for some reason you didn’t get it right the first time.

There is a lot to be said for simply sitting still without moving a muscle, and while this may sound like a great excuse for sloth, there is a point to it. Watching and waiting for something to happen is one of the best things a naturalist can do in the field, and this applies just as much to other wildlife as it does to birds. Obviously you can increase your chances of seeing something interesting by knowing some of the habits of the creature you are trying to watch, but simply doing nothing in the right place at the right time is a technique that has never failed to amaze me. I’ve had Badgers run into my legs and knock them from under me, I’ve nearly been stepped on by a Giraffe, I’ve had a Grizzly Bear eat a fish so close I got an eyeful of milt and I’ve had a Sparrowhawk pluck a thrush before my very eyes.

The technique is universal, and I remember once having a chat with a naturalist about someone who had named the art of sitting still. The problem is that I cannot remember who it was. Recent conversations seem to suggest a Canadian called Ernest Thompson Seton, though a correspondent of mine who is a member of the Seton Trust has never heard of it but agrees that if it isn’t called the Seton technique it should be. So you may well have heard it here first: ‘The Seton technique, simply sit and wait!’

Sitting and waiting works even better if you cannot be seen by your quarry. There are purpose-built bird hides, or blinds, on many nature reserves now; they can be anything from a draughty shed to a centrally heated, double-glazed monstrosity complete with coffee machine. But the object is the same – they allow you to be human without disturbing the animals you have come to watch. For me the best thing about them is the social scene within: hides are simply the best place to meet other ‘birders’, from full-blown bird nuts to casual Sunday-afternoon binocular claspers. The hide becomes one big ‘superbirder’ with as many pairs of eyes as there are people gathered inside, and the more eyes there are looking the less chance a bird has of sneaking past without being seen.

Remember hide etiquette, though – keep the noise down, do not forget to share the space and do not, whatever you do, stick your hands out of the slots to point at something. I’ve seen it happen, and the person who scares off a huge flock of mixed waterfowl by doing this will wish they had wings, too! One other thing – when you leave, shut the viewing ‘slots’ behind you and don’t let the door slam.

At the other end of the hide or blind scale are the ones a versatile naturalist will want to build and position themselves. There were once a couple of nature photographers, the Kearton brothers, who used to get close to animals in many remarkable and bizarre ways such as making model cows and sheep to hide themselves and their cameras in. While there is no limit to how inventive you can be in order to achieve your goal, simpler options are available, and what you opt for depends on your needs.

Probably the most basic form of hide and one you can carry around with you is a bit of military camouflage scrim. Scrim is that netting with various bits and pieces stuck to it, used to break up your outline. Its big advantage is that it is lightweight and you can carry it in your pack. If you stumble across a situation where you need to vanish, simply throw it over yourself or fashion a basic support from the available vegetation and you have a hide. The disadvantages are that it is flimsy, will blow around and doesn’t protect you from the elements.

You can achieve similar results with natural materials such as bent branches, string and leafy vegetation or, if you want something more robust and permanent, incorporate waterproof canvas and scrim, add a chair and a flask of hot coffee and you have a set-up that should allow you to outlast even the most patience-testing bird.

The other option is the ‘throw money at it’ one. There are hides on the market that are practically camouflaged tents and come in a huge range of designs to suit an equally diverse range of budgets.

It’s lucky for the naturalist that birds cannot count – even smart birds like Ravens (Corvus corax) have trouble with mental arithmetic. If you are planning to spend some time in a hide which has an unprotected approach that means you will be seen by your quarry, rope a friend in to walk you to the door. If you both go in, wait for a minute or two and then your friend goes back; the animals will perceive the threat as having left. You can now relax and get down to watching the animals as they go about their business.

Do your research before building or locating your hide. Get to know the area and how the animals are using it. I once spent a long time creating what I thought was a hide masterpiece, perfectly positioned close to the holt of a Giant Otter (Pteronura brasiliensis). After waiting for several hours, I became aware of a rumbling noise that appeared to come from below my feet. It wasn’t until a strong smell of fish started permeating the hide that I looked out to find that the ‘back’ door to this otter’s holt (actually its front door, as it turned out) opened behind my hide. The rumbling was the otters passing backwards and forwards beneath my feet and the smell of fish came from what they were having for dinner while I was pointing in the other direction!

Make a note of the prevailing wind direction of your site and try to pitch your position downwind. This is not as important with birds as it is with mammals, but is still worth taking into account: you may have come for the Oystercatchers, but if an otter was to turn up, you would kick yourself if it sussed you out and ran away.

Prepare yourself for your period of isolation. Take food and a drink of a suitable temperature. Hides can get surprisingly hot or cold, and a drink will help alleviate discomfort. Once inside your hide, do not be lured into a false sense of security. You may be hidden, but any noise you make will pass through the flimsy material of the hide. Avoid rustling clothes, crisp packets and food wrappers. Opt for a quiet sandwich instead. When it’s time to go home, always leave as quietly as you arrived.

Many bird species find advantage in flocking together for the winter. This whole mass-roosting thing is a bit of an enigma. The first obvious theory is communal thermal regulation – combining lots of little bodies to form one large one with a relatively smaller surface area. This would make sense for a lot of small birds, but if you look at roosts of Pied Wagtails (Motacilla alba) and Starlings you will see that the birds are not huddled but very spaced out, and so the theory doesn’t seem to work there. Those desperate to conserve warmth, such as Wrens and several members of the tit family, will jam themselves into old nestboxes and crevices, as I described earlier.

So what is going on with the big roosts of birds that aggregate for the night only? An obvious advantage is safety in numbers – lots of birds milling around makes for confusing hunting, and if you watch a flock of Dunlin seethe, shimmer and condense at the attack of a Peregrine, you can understand how this works. This would apply equally to the activities of Sparrowhawks (Accipiter nisus) and Tawny Owls, which are regularly seen having a pop at big roosts. Added to the confusion is the fact that, with so many birds to eat, all the predators in a small area are sated quickly, and each individual in a flock stands less chance of being nobbled.

Another theory is that a lot of the bird equivalent of gossiping occurs at a roost, each bird communicating with others if they have split up during the day to feed, as Starlings do. Those returning to the roost with a full crop somehow by appearance or sound pass on the message that they have fed well and that any less successful birds may benefit from joining up with them the next day.

For much of the year woodlands, copses and hedgerows act as living leafy shrouds, obscuring the details of private lives. During the bare winter months, however, things become more transparent. Back lit against a watery grey sky, the trees not only reveal their own profiles but also betray many of the summer’s secrets.

Birds’ nests are among the things that are revealed. It’s taboo to go looking for these in spring and high summer when they are fulfilling their function, but now that they lie vacant – of birds, at least – the amateur naturalist can revel in them.

Dense bundles of twigs and vegetation give away where birds’ nests were built, and so if you failed to discover where that Long-tailed Tit (Aegithalos caudatus) was heading with all those strands of horsehair and moss back in the summer, now is your chance. If this sounds like a waste of time, bear in mind that some birds return to the same areas year after year or at least select the same habitat or height, and so finding and identifying nests and their positions now can stand you in good stead next year.

At first and to the inexperienced eye, one nest may look very much like the next, just a tangle of sticks, straw and a bit of mud. But with a little practice, a touch of guesswork and the usual healthy helping of dogged persistence, you can soon start linking them to their avian originators.

Distinctive constructions such as the large, loose-domed stick nests of Magpies, the tree-top communities of platforms constructed by Rooks or the solitary efforts of Carrion Crows are relatively easy even from a distance. Slightly more taxing are the similar-sized nests of various garden birds such as Blackbirds (Turdus merula) and Song Thrushes (Turdus philomelos), but these can be separated on constructional merits. Song Thrushes are unique among British birds in having a hard lining of mud to their nests, while Blackbirds use mud in the construction but actually line the nest with fine grasses. The masterpieces of Wrens look like moss footballs, each with a hole punched in its side, built close to stumps and in dense vegetation.

After some searching you will discover the small cup-shaped nests of finches – often made of finer materials than the thrushes’ such as grass, hair, wool and moss. Greenfinches (Carduelis chloris) and Chaffinches are less fussy than their relatives about location; their nests are the ones you are most likely to find in a garden hedge – the Chaffinch’s is a rather neater cup-shape that the Greenfinch’s. For the other finches, you need to look a little higher, either in the forks of trees close to the trunk or towards the ends of branches.

While nest-watching, look out for stashes of seeds and fruits, as hedgerow nests are often used by squatters such as voles and Wood Mice. And, just as we have a microcosm of life in our own households, so do birds. Take a disused nest home, break it open on a sheet of white paper and watch as pseudoscorpions, spiders and mites come tottering out.

For the observant masterclass of nest-spotters, look for the bored-out nest holes created by woodpeckers. Green (Picus viridis) and Great Spotted Woodpeckers (Dendrocopos major) have a nest entrance of around 7–8cm (2¾–3in) in diameter, while the Lesser Spotted (Dendrocopos minor) has a tiny doorway of about 4 cm (1½in). But there is more to this than the size of the holes. Green Woodpeckers prefer to knock holes in healthy-looking trees with rotten hearts, Great Spotted tend to use trees that are obviously on the way out and Lesser Spotted nest holes are often higher and on the underside of a sloping branch.

It’s not just birds’ architectural activities that you are likely to come across whilst scanning the lofty levels of a woodland. You may well notice the summer drey of a Grey Squirrel, but the chances are that you wouldn’t know that was what it was, as they resemble a hollowed-out crow’s nest built high and out on the branches. Larger and much more distinctive is the dense winter drey, also used as a nursery. This is often constructed with leafy twigs, lined with mosses and grass and built close to the trunk where it is less prone to the buffeting of gales.

Another ornithological extra worth looking for requires first identifying a tree. Old parks and churchyards are the best places in the UK to find mature Wellingtonia trees. These unmistakable giant conifers native to California have a soft, deep and fibrous bark. Check this over in daylight, and the chances are you will find small oval depressions in the bark, made more obvious by a trickle of white bird droppings below each one. Return on a cold night, and you will find these plugged with the tiny tawny-streaked bodies of Treecreepers (Certhia familiaris). The birds hollow out these customised and insulated snugs, and a single tree can attract birds from all over the neighbourhood seeking sanctuary from the cold; as many as 25 can be seen on one large tree.

From little brown jobs (LBJs) to large white ones, unexpected animals can throw the ornithological world into turmoil at certain seasons. Headlands can be as busy as a bank holiday weekend at Heathrow Airport when the autumn migration is in full swing, what with winter visitors flying in, summer breeders checking out, a few species in transit landing for a refuel and fuselage check and individuals who alight lost, way off their intended course.

Despite the many clues – Swallows gathering on wires, the disappearance of that Spotted Flycatcher that was always in the garden, the emptiness echoing in the shrubs, the lack of calls from Willow Warblers, Common Whitethroats (Sylvia communis) and Chiffchaffs (Phylloscopus collybita) – the autumn migration is not as obvious as its spring equivalent. In spring the birds are driven by a lustful urgency to set up territories and get a head start on the breeding season; by autumn the pressure is off and the outflux is a gradual one. This apathy is obvious in many streets; while some nests of House Martins (Delichon urbica) lie abandoned, their owners already on their way, others still have their entrances stuffed full of the pied ‘yippering’ heads of the last generation of the year.

Millions of birds that have visited for the summer breeding season and their offspring are southbound again. Many that have boarded further north, in places such as Iceland, Greenland and Scandinavia, either join us for the winter or use our temperate zones like convenient avian motorway services before continuing south to the Mediterranean and Africa.

If you don’t live near moorland and fancy seeing a Ring Ouzel, or want to learn your warblers all in one day, are turned on by rarities such as a Red-breasted Flycatcher (Ficedula parva) or simply wish to witness the spectacle of Swallows doing what they are famous for, the time to act is now. Choose your day carefully and according to the weather. For best results, think like a bird that has to conserve its resources; early mornings on days with a inshore wind are best, as any birds wanting to leave land are likely to ‘bunch up’, waiting for more favourable weather. These conditions also help birds travelling the opposite way and heading for landfall.

Do not be put off by the thought of being surrounded by thousands of unidentifiable LBJs. The beauty of the autumn migration is that, with a bit of luck, you will get plenty of easy ‘spots’. A good wind may carry with it the first ‘fall’ of Redwings (Turdus iliacus) and Fieldfares (T. pilaris) on the same day that scores of Pied (Ficedula hypoleuca) and Spotted Flycatchers, whitethroats, Garden Warblers (Sylvia borin), Wheatears (Oenanthe oenanthe) and Whinchats (Saxicola rubetra) are queuing to check out. In the west it is not unknown for a few treats to turn up – such as Bluethroats (Luscinia svecica), Wrynecks (Jynx torquilla) or the ungainly bulk of an incoming Woodcock (Scolopax rusticola) or two.

Take advantage of vantage points

Many birds, such as these White Stork, migrate along well-known flight paths making watching visible migration ‘viz migging’ possible.

The knack of beholding the migration spectacle is simply being in the right place at the right time. And the right place is one of the many ‘sticky-out’ bits: headlands, bills, mulls and peninsulas become the focal points for birds that are passing through, funnelling those moving over land to the shortest oversea jumps and providing good vantage points from which to spy seabirds passing offshore.